Reading was the ability to understand and speak written words. One could read for educational purposes, or for pleasure and relaxation. Not being able to read could lead to ignorance.
Vissian cogenitors were not allowed to learn to read. In 2153, Trip Tucker tried to teach Charles how to read, only to face censure from both the other Vissians and Captain Jonathan Archer for interfering. (ENT: "Cogenitor")
Later that year, Bethany illegally taught Skagaran children how to read. Sheriff MacReady felt that this would lead to their learning that the Humans had initially been dominated by the Skagarans on their colony planet. (ENT: "North Star")
In 2267, after her memory was wiped by the probe Nomad, Nyota Uhura had to re-learn how to read with the help of nurse Christine Chapel and a first grade reader. (TOS: "The Changeling")
In 2269, Spock explained his familiarity withAlice Through the Looking Glass as being due to his mother having read Lewis Carroll's works. (TAS: "Once Upon a Planet")
In 2369, while visiting her father during Jean-Luc Picard's interrogation, Jil Orra asked if he would read to her that night. Madred promised he would. (TNG: "Chain of Command, Part II")
Some documents were required reading at Starfleet Academy. These included Doctor Roger Korby's translation of medical records found in the Orion ruins (TOS: "What Are Little Girls Made Of?"), Garth of Izar's exploits, including his victory at the Battle of Axanar (TOS: "Whom Gods Destroy"), Judge Aaron Satie's judgments (TNG: "The Drumhead"), and The Fall of Kang. (DS9: "Second Sight")
By 2372, Benjamin Sisko's psychographic profile was required reading for Vorta field supervisors. (DS9: "To the Death")